Re: [PATCH] Provide extension hint for aarch64 target (PR driver/83193).

[Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>]

Hi Martin,

On 18/07/18 16:49, Martin Liška wrote:
> Hi.
>
> This patch improves aarch64 feature modifier hints.
>
> May I please ask ARM folks to test the patch?
> Thanks,
> Martin
>

I've bootstrapped and tested it on aarch64-none-linux-gnu and I didn't see any problems.
I like the functionality! It is definitely an improvement to the user experience.

I'm not an aarch64 maintainer but I have some comments on the patch below.

Thanks,
Kyrill

> gcc/ChangeLog:
>
> 2018-07-18  Martin Liska  <mliska@suse.cz>
>
>         PR driver/83193
>         * common/config/aarch64/aarch64-common.c (aarch64_parse_extension):
>         Set invalid_extension when there's any.
>         (aarch64_get_all_extension_candidates): New function.
>         (aarch64_rewrite_selected_cpu): Pass NULL as new argument.
>         * config/aarch64/aarch64-protos.h (aarch64_get_all_extension_candidates):
>         Declare new function.
>         * config/aarch64/aarch64.c (aarch64_parse_arch): Record
>         invalid_feature.
>         (aarch64_parse_cpu): Likewise.
>         (aarch64_print_hint_for_feature_modifier): New.
>         (aarch64_validate_mcpu): Record invalid feature modifier
>         and print hint for it.
>         (aarch64_validate_march): Likewise.
>         (aarch64_handle_attr_arch): Likewise.
>         (aarch64_handle_attr_cpu): Likewise.
>         (aarch64_handle_attr_isa_flags): Likewise.
>
> gcc/testsuite/ChangeLog:
>
> 2018-07-18  Martin Liska  <mliska@suse.cz>
>
>         PR driver/83193
>         * gcc.target/aarch64/spellcheck_7.c: New test.
>         * gcc.target/aarch64/spellcheck_8.c: New test.
> ---
>  gcc/common/config/aarch64/aarch64-common.c    | 20 +++++-
>  gcc/config/aarch64/aarch64-protos.h           |  4 +-
>  gcc/config/aarch64/aarch64.c                  | 67 +++++++++++++++----
>  .../gcc.target/aarch64/spellcheck_7.c         | 11 +++
>  .../gcc.target/aarch64/spellcheck_8.c         | 12 ++++
>  5 files changed, 97 insertions(+), 17 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/aarch64/spellcheck_7.c
>  create mode 100644 gcc/testsuite/gcc.target/aarch64/spellcheck_8.c
>
>

diff --git a/gcc/common/config/aarch64/aarch64-common.c b/gcc/common/config/aarch64/aarch64-common.c
index 292fb818705..c2994514004 100644
--- a/gcc/common/config/aarch64/aarch64-common.c
+++ b/gcc/common/config/aarch64/aarch64-common.c
@@ -175,7 +175,8 @@ static const struct arch_to_arch_name all_architectures[] =
     aarch64_parse_opt_result describing the result.  */
  
  enum aarch64_parse_opt_result
-aarch64_parse_extension (const char *str, unsigned long *isa_flags)
+aarch64_parse_extension (const char *str, unsigned long *isa_flags,
+			 char **invalid_extension)
  {

Please document the new argument in the function comment. Same for all the other parsing functions that you extend in the patch.
In particular, I'd like to see a comment on who allocates the memory for the string and who is responsible for freeing it.

+/* Append all extension candidates and put them to CANDIDATES vector.  */
+

Given the implementation below, how about:
"Append all architecture extension candidates to the CANDIDATES vector." ?

+void
+aarch64_get_all_extension_candidates (auto_vec<const char *> *candidates)
+{
+  const struct aarch64_option_extension *opt;
+  for (opt = all_extensions; opt->name != NULL; opt++)
+    candidates->safe_push (opt->name);
+}
+

<snip>

+
+/* Print a hint with a suggestion for a feature modifier name
+   that most closely resembles what the user passed in STR.  */
+
+void
+aarch64_print_hint_for_feature_modifier (const char *str)
+{


Elsewhere in the backend and this patch as well we call them extensions rather than feature modifiers.
Let's be consistent: aarch64_print_hint_for_extension would is my suggestion

+  auto_vec<const char *> candidates;
+  aarch64_get_all_extension_candidates (&candidates);
+  char *s;
+  const char *hint = candidates_list_and_hint (str, s, candidates);
+  if (hint)
+    inform (input_location, "valid arguments are: %s;"
+			     " did you mean %qs?", s, hint);
+  else
+    inform (input_location, "valid arguments are: %s;", s);
+
+  XDELETEVEC (s);
+}
+

diff --git a/gcc/testsuite/gcc.target/aarch64/spellcheck_7.c b/gcc/testsuite/gcc.target/aarch64/spellcheck_7.c
new file mode 100644
index 00000000000..1350b865162
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/spellcheck_7.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-skip-if "" { *-*-* } { "-march=*" } { "" } } */

Another way that the extensions are used is with -mcpu. For example -mcpu=cortex-a57+crypto.
So you'll need to skip if -mcpu is given as well.
And we'll want a test for -mcpu error-checking as well.

+/* { dg-options "-march=armv8-a+typo" } */
+
+void
+foo ()
+{
+}
+